Or, Exact...take advantage of your competitor's free advertising. He has used his advertising to sell your customers. If they ask about it, they are ready to buy--pre-sold.
Let them give you their money. And thank them.

Are you planning on a liquid or granular application?

Point out how Milorganite has .58 percent sulfur. And you can give them the added benefits of both. Then you are like your competitors, but better.

You could include a micronutrient package with sulfur, because that might actually do some good. Or perhaps apply your sulfur as sulfur-coated urea. Or calcium sulfate (gypsum), if your soils might need it on the average. Or get them to allow you to include spreading seed that is resistant to snowmold.